Influenza claimed the lives of 52 more Californians during the first week of peak flu season, driving the number of flu-related deaths nearly 50 percent higher than last year's entire total by the end of January.

In addition to the deaths reported by the State Friday, Santa Clara County reported the deaths of a 43-year-old and a 54-year-old man, bringing the county's total number to 10, the fifth-highest county total in the state. The nine Bay Area counties and Santa Cruz County have reported 35 flu-related deaths this season; after Santa Clara County, the highest Bay Area total is in Contra Costa County, which has had five flu-related deaths so far.

State officials confirmed a total of 147 flu-related deaths Friday morning, with an additional 44 deaths remaining under investigation, said Dr. Ron Chapman, director of the California Department of Public Health. The confirmation of those cases as flu-related would push the number of deaths to 191 in residents under 65, four of which were confirmed as children.

Only 106 flu deaths were reported during the entire 2012-2013 season, a total reached in one month alone during the current flu season.

The H1N1 virus -- the swine flu bug -- is circulating through susceptible groups, especially among a younger generation that often goes without vaccinations and had not been exposed to this strain, health authorities said. H1N1 has largely replaced last year's H3N2 strain and has already killed nearly 50 percent more people than last year's total.

Those at highest risk, including the elderly, pregnant women, infants, or those with other underlying health conditions are urged to contact their physician immediately if they experience symptoms such as fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches or fatigue.

"This influenza season continues to be a severe one, as the increasing number of influenza-related deaths indicates," Chapman said. "I urge all Californians to get vaccinated, because it is the best defense against influenza."

Flu vaccines remain readily available, and no widespread shortages of antivirals have been reported. CDPH officials will continue to closely monitor flu activity, as well as the supply of vaccines, antivirals and other medical resources.